Search Results (171)

Microfluidic systems have become a hot topic in Micro-Electro-Mechanical System (MEMS) research, with micropumps serving as a key element due to their role in determining structural and flow dynamics within these systems. This study aims to analyze the influence of different structural obstacles within microfluidics on micropump efficiency and offer guidance for improving microfluidic system designs. In this context, a MEMS-based micropump valve structure was developed, and simulations were conducted to examine the effects of the valve on microfluidic oscillations. The research explored various configurations, including valve positions and quantities, yielding valuable insights for optimizing microfluidic transport mechanisms at the microscale. Full article

Microfluidic devices rely on precise fluid control to enable complex operations in diagnostics, chemical synthesis, and biological research. Central to this control are microvalves, which regulate on-chip flow but require flexible membranes for active operation. While the laser cutting of thermoplastics offers a fast, automated method for fabricating rigid microfluidic components, integrating flexible elements like valves and pumps remains a key challenge. Thermoplastic polyurethane (TPU) membranes have been adopted to address this need but are costly and difficult to procure reliably. In this study, we present commercial food-wrap film (FWF) as a low-cost, widely available alternative membrane material. We demonstrate FWF’s compatibility with laser-cut thermoplastic microfluidic devices by successfully fabricating Quake-style valves and peristaltic pumps. FWF valves maintained reliable sealing at 40 psi, maintained stable flow rates of ~1.33 μL/min during peristaltic operation, and sustained over one million continuous actuation cycles without performance degradation. Burst pressure testing confirmed robustness up to 60 psi. Additionally, FWF’s thermal resistance up to 140 °C enabled effective thermal bonding with PMMA layers, simplifying device assembly. These results establish FWF as a viable substitute for TPU membranes, offering an accessible and scalable solution for microfluidic device fabrication, particularly in resource-limited settings where TPU availability is constrained. Full article

The Tesla valve (TV) is a valvular conduit that allows fluid to flow in one direction while restricting flow in the opposite direction, making it useful for enhancing fluid control in the field of microfluidics. Our previous research has found that the enhancement of multi-stage TVs’ diodicity is mainly due to the interstage non-uniform flow field. In this study, we introduce baffles in different positions to discover the effect of non-uniform flow field on single-stage TV’s diodicity. We employed 3D printing technology to fabricate a TV for experimental purposes. The experimental data revealed that flow distortion can lead to an increase in diodicity of up to 30% for the studied single-stage TV. Concurrently, we conducted simulations, establishing a simulation model, and then compared the results of the simulation model with the experimental outcomes. This comparison demonstrated the reliability of the model. The detailed analysis indicates that the high-performance optimization is attributed to the baffle design, which preferentially directs fluid into the arc channel, enhancing reverse flow resistance while minimally affecting forward flow resistance. These findings provide valuable strategies for the optimization of the design and performance prediction of single-stage Tesla valves. Full article

This study presents a pneumatic proportional pressure valve employing a silicon microfluidic chip (SMC) integrated with a V-shaped electrothermal microactuator, aiming to address the limitations of traditional solenoid-based valves in miniaturization and high-precision control. The SMC, fabricated via MEMS technology, leverages the thermal expansion of microactuator ribs to regulate pressure through adjustable orifices. A first-order transfer function between input voltage and displacement of the microactuator was derived through theoretical modeling and validated via COMSOL Multiphysics 5.2a simulations. Key geometric parameters of the actuator ribs—cross-section, number, inclination angle, width, span length and thickness—were analyzed for their influence on lever mechanism displacement, actuator displacement, static gain and time constant. AMESim 16.0-based simulations of single- and dual-chip valve structures revealed that increasing ζ shortens step-response rise time, while reducing τ improves hysteresis. Experimental validation confirmed the valve’s static and dynamic performance, achieving a step-response rise time of <40 ms, linearity within the 30–60% input voltage range, and effective tracking of sinusoidal control signals up to 8 Hz with a maximum pressure deviation of 0.015 MPa. The work underscores the potential of MEMS-based actuators in advancing compact pneumatic systems, offering a viable alternative to conventional solenoids. Key innovations include geometry-driven actuator optimization and dual-chip integration, providing insights into high-precision, low-cost pneumatic control solutions. Full article

The Polydimethylsiloxane (PDMS) SlipChip is a microfluidic platform enabling fluid manipulation without pumps or valves, simplifying operation and reducing reagent use. High-viscosity silicone oils (e.g., 5000–10,000 cSt) improve sealing but frequently block microfluidic channels, reducing usability. In contrast, low-viscosity oils (50–100 cSt) reduce blockages but may compromise sealing. This study addresses these challenges by optimizing the viscosity of silicone oil and the curing conditions of PDMS. Low-viscosity silicone oil (50 cSt) was identified as optimal, ensuring smooth slipping and reliable sealing without blockages. Curing conditions were also adjusted to balance adhesion and stiffness as follows: lower temperatures (50–60 °C) enhanced van der Waals adhesion, while higher temperatures (80 °C) increased stiffness. A mixed curing approach (80 °C for the top layer and 60 °C for the bottom layer) further improved performance. Biocompatibility testing using human osteosarcoma cells demonstrated minimal cytotoxicity with 50 cSt oil, supporting cell viability (95%) comparable to traditional multiwell plates. These findings provide practical guidelines for fabricating reliable and biocompatible SlipChips. Full article

As one of the major rice fungal diseases, blast poses a serious threat to the yield and quality of rice globally. It is caused by the pathogen Pyricularia grisea. Therefore, the development of rapid, accurate, and portable microfluidic detection system for Pyricularia grisea is important for the control of rice blast. This study presents an integrated microfluidic detection system for the rapid and sensitive detection of Pyricularia grisea using the LAMP detection method. The microfluidic detection system includes a microfluidic chip, a temperature control module, and an OpenMv camera. The micro-mixing channels with shear structures improve the mixing efficiency to about 98%. Flow-blocking valves are used to reduce reagent loss in the reaction chamber. The temperature control module is used to heat the reaction chamber, maintaining a stable temperature of 65 °C. The microfluidic chip detection chamber is used for image inspection using an OpenMv camera. The developed system can detect Pyricularia grisea in the range of 10 copies/μL–10⁵ copies/μL within 45 min. Specificity and interference experiments were performed on Pyricularia grisea, validating the method’s good reliability. This LAMP detection system based on a microfluidic chip has strong potential in the early and effective detection of rice blast. Full article

Microfluidics is a technology that manipulates liquids on the scales ranging from microliters to femtoliters. Such low volumes require precise control over pressures that drive their flow into the microfluidic chips. This article describes a custom-built pressure controller for driving microfluidic chips. The pressure controller features piezoelectrically controlled pressure regulation valves. As an open-source system, it offers high customizability and allows users to modify almost every aspect. The cost is roughly a third of what similar, alternative, commercially available piezoelectrically controlled pressure regulators could be purchased for. The measured output pressure values of the device vary less than 0.7% from the device’s reported pressure values when the requested pressure is between −380 and 380 mbar. Importantly, the output pressure the device creates fluctuates only ±0.2 mbar when the pressure is cycled between 10 and 500 mbar. The pressure reading accuracy and stability validation suggest that the device is highly feasible for many advanced (low-pressure) microfluidic applications. Here, we compare the main features of our device to commercially and non-commercially available alternatives and further demonstrate the device’s performance and accessibility in successful microfluidic hydrodynamic focusing (MHF)-based synthesis of large unilamellar vesicles (LUVs). Full article

A versatile and modular microfluidic system for cell co-culture has been developed. Microfluidic chips, each featuring dual compartments separated by a porous membrane, have been fabricated and assembled within the system to facilitate fluidic interconnection and cell–cell communication through the chip assembly. A set of fluidic valves has been successfully integrated to regulate the flow through the chip assembly. The system allows for chip assembly in various arrangements, including in parallel, in series, and complex connections. Individual chips can be interconnected or disconnected within the system at any time. Moreover, the spatial order and orientation of the chips can be adjusted as needed, enabling the study of different cell–cell arrangements and the impact of the presence or absence of specific cell types. The utility of the system has been evaluated by culturing and interconnecting multi-monolayers of intestinal epithelial cells as a model of the complex cellular system. Epithelial monolayers were grown in multiple chips and interconnected in various configurations. The transepithelial electrical resistance and permeability profiles were investigated in detail for these configurations upon treatment of the cells with dextran sulfate sodium. Immune cells were stimulated through the epithelial layers and the expression of inflammatory cytokines was detected. This miniaturized platform offers controlled conditions for co-culturing key cellular components and assessing potential therapeutic agents in a physiologically relevant setting. Full article

In nature, dynamic liquid interfaces play a vital role in regulating gas transport, as exemplified by the adaptive mechanisms of plant stomata and the liquid-lined alveoli, which enable efficient gas exchange through reversible opening and closing. These biological processes provide profound insights into the design of advanced gas control technologies. Inspired by these natural systems, liquid gating membranes have been developed utilizing capillary-stabilized liquids to achieve precise fluid regulation. These membranes offer unique advantages of rapid responses, stain resistance, and high energy efficiency. Particularly, they break through the limitations of traditional solid, porous membranes in gas transport. This perspective introduces bioinspired liquid gating gas valve membranes (LGVMs), emphasizing their opening/closing mechanism. It highlights how external stimuli can be exploited to enable advanced, multi-level gas control through active or passive regulation strategies. Diverse applications in gas flow regulation and selective gas transport are discussed. While challenges related to precise controllability, long-term stability, and scalable production persist, these advancements unlock significant opportunities for groundbreaking innovations across diverse fields, including gas purification, microfluidics, medical diagnostics, and energy harvesting technologies. Full article

A two-dimensional array of microfluidic ports with remote-controlled valve actuation is of great interest for applications involving localized chemical stimulation. Herein, a macroporous silicon-based platform where each pore contains an independently controllable valve made from poly(N-isopropylacrylamide) (PNIPAM) brushes is proposed. These valves are coated with silica-encapsulated gold nanorods (GNRs) for NIR-actuated switching capability. The layer-by-layer (LBL) electrostatic deposition technique was used to attach the GNRs to the PNIPAM brushes. The deposition of GNRs was confirmed by dark-field optical microscopy, and the localized surface plasmon resonance (LSPR) of the deposited GNRs was analyzed using UV-Vis spectra. To evaluate the chemical release behaviors, fluorescein dye was employed as a model substance. The chemical release properties, like OFF-state diffusion through the valve, the ratio between ON-state and OFF-state chemical release, and the rapidness of chemical modulation of the valve, were investigated, varying the PNIPAM brush thickness. The results indicate that enhancing the thickness of the PNIPAM brush in our platform improves control over the chemical modulation properties. However, excessive increases in brush length may lead to entanglement, which negatively impacts the chemical modulation efficiency. Full article

Accurate fluid management in microfluidic-based point-of-care testing (POCT) devices is critical. Fluids must be gated and directed in precise sequences to facilitate desired biochemical reactions and signal detection. Pneumatic valves are widely utilized for fluid gating due to their flexibility and simplicity. However, the development of reliable normally closed pneumatic valves remains challenging, despite their increasing demand in advanced POCT applications to prevent uncontrolled fluid flow. Existing normally closed valves often suffer from poor reliability and lack precise control over fluid opening pressure, due to the uncontrolled stretching of the elastomer during assembly. In this study, we propose and develop a robust method for normally closed valves. By precisely controlling the pre-stretching of the elastomer, we achieve reliable valve closure and accurate control of the opening pressure. A robust normally closed valve was designed and fabricated, and its pneumatic opening pressure was systematically studied. Experimental validations were conducted to demonstrate the reliability and effectiveness of the proposed design. Full article

Despite major advances in the field of actuator technology for microsystems, miniaturized microfluidic actuation systems for mobile devices are still not common in the market. We present a micropump concept and an associated mass flow sensor design, which, in combination, have the potential to form the basis for an integrated microfluidic development platform for microfluidic systems in general and microdosing systems in particular. The micropump combines the use of active valves with an electrostatic drive principle for the pump membrane and the valves, respectively. With a size of only 1.86 mm × 1.86 mm × 0.3 mm, the first prototypes are capable of pumping gaseous media at flow rates of up to 110 μL/min. A specific feature of the presented micropump is that the pumping direction is perpendicular to the chip surface. The corresponding flow sensor combines the principle of hot-wire anemometry with a very small footprint of only 1.4 mm × 1.4 mm × 0.4 mm. The main innovation is that the hot wires are fixed inside a through-hole in the substrate of the microchip, so that the flow direction of the fluid to be measured is perpendicular to the chip surface, which enables direct integration with the presented micropump. Detection thresholds of around 10 μL/min and measuring ranges of up to 20 mL/min can be achieved with the first prototypes, without dedicated evaluation electronics. Full article

Microfluidics are crucial for managing small-volume analytical solutions for various applications, such as disease diagnostics, drug efficacy testing, chemical analysis, and water quality monitoring. The precise control of flow control devices can generate diverse flow patterns using pneumatic control with solenoid valves and a microcontroller. This system enables the active modulation of the pneumatic pressure through Arduino programming of the solenoid valves connected to the pressure source. Additionally, the incorporation of solenoid valve sets allows for multichannel control, enabling simultaneous creation and manipulation of various microflows at a low cost. The proposed microfluidic flow controller facilitates accurate flow regulation, especially through periodic flow modulation beneficial for droplet generation and continuous production of microdroplets of different sizes. Overall, we expect the proposed microfluidic flow controller to drive innovative advancements in technology and medicine owing to its engineering precision and versatility. Full article

Controlling the fluids in centrifugal microfluidic chips for precise sequential release is critical for multi-step reactions and immunoassays. Currently, the traditional methods of liquid sequential release mainly rely on various types of microvalves, which face the problems of complex operation and high costs. Here, this work presents a method for driving liquid release using the Euler force. Under continuous acceleration and deceleration, the centrifugal and Euler forces can transfer the liquid from the sample chamber to the collection chamber. The liquid sequential release mechanism based on the Euler force was analyzed, which showed that the angular acceleration is key to the liquid release. Then, the geometrical parameters affecting the angular acceleration of complete release were investigated and simulated. Finally, based on the relationship between the geometrical parameters of the connecting channels and the angular acceleration of complete release, a simple and precise sequential release structure was designed, which allowed for a sequential and stable transfer of the liquid into the reaction chamber. The results showed that the proposed method is capable of transferring liquid, and its simple structure, low manufacturing cost, and ease of operation enable precise sequential liquid release in centrifugal microfluidic platforms. Full article

In order to meet the requirements of microfluidic transport in the fields of medical, health, and microelectromechanical integration, a valve-less piezoelectric pump with a tapered cross-sectional vibrator was designed according to the bionic principles of fish swimming. Through theoretical analysis, the pattern of fluid flow in the pump chamber caused by the vibration of the piezoelectric vibrator was derived. The flow field of the piezoelectric pump was analyzed through simulation based on multiple physical fields coupling using the software of COMSOL Multiphysics (version 6.1). The velocity field distribution and its change law were obtained, and the fluid disturbance and instantaneous motion suppression phenomena were acquired as well. Based on the analysis of flow field streamline, the rule of generating vortexes was found. Thus, the driving mechanism of the vibrator with the tapered cross-section, which was consistent with the swimming principle of a fish tail, was verified. A prototype pump was made, and the pump performance was tested. The experimental data showed that the tested flow rate changed in the same trend as the simulated flow rate. When the driving voltage was 150 V and the driving frequency was 588 Hz, the pump achieved a maximum output flow rate of 367.7 mL/min. These results indicated that the piezoelectric pump with the tapered cross-sectional vibrator has great potential of fluid transportation. Full article